Given all the great responses I've been getting on my idle problems, I would NOT
suspect the oxygen sensor just yet.  Sounds more like the O2 sensor was trying to
compensate for a problem that exists elsewhere in the system.  I'd look at the
fast idle first.  Disconnecting the ISV won't tell you too much, because that just
means the idle stabizer control unit doesn't have a device to control.  I'd
troubleshoot the ISV . . . is it vibrating/buzzing . . . clean the heck out of it
with carb cleaner, then see what happens with it connected (keep the O2 sensor
disconnected till you solve the fast idle problem).  If it's still a problem, you
could have a bad ISCU.  Best thing to do, swap in a known good ISV, test, then
swap in a known good ISCU.  If problem is gone, replace both.  According to
several people who communicated to me about my problems, if the ISV is bad and you
replace the ISCU, the ISV could destroy the new ISCU.

There are other things that could cause warm-temp. operating problems:  Temp II
sensor, plugged cat. converter, others . . .

Good luck,
Marc Perdue

David Brodbeck wrote:

> On Thu, 3 Apr 2003, Warner, Jeff (DSIO) wrote:
>
> > Keep it running long enough to see that it's running real rich
> > with black smoke, rough and won't easily rev up.  Shut it off (here I made a
> > mistake forgetting about how with the Vanagon Syndrome I may have been able
> > to simply restart it and the problem would be gone), I disconnected the OXS
> > and restarted and it's fine except it's idling fast.
>
> Bad oxygen sensor?
>
> David Brodbeck, N8SRE
> '82 Diesel Westfalia
> '94 Honda Civic Si